header {
    height: 50px;
    line-height: 50px;
    padding-left: 15px;
    font-size: 16px;
}
nav {
    width: 100%;
    overflow: hidden;
    height: 51px;
    line-height: 50px;
    background: #fff;
    font-size: 16px;
}
ul {list-style: none;}
ul li {
    float: left;
    width: 33.33%;
    text-align: center;
    cursor: pointer;
}
ul li.active {
    border-bottom: 1px solid blue;
}
.con {
    width: 100%;
    height: 100%;
}
.gray {
    width: 100%;
    height: 10px;
    background: gray;
}